Quadrature error is one of the primary factors that limit the performance of micromachined sensors such as gyroscopes. Considering the relative magnitudes of the drive and sense oscillations, even an extremely small part of the drive motion coupling into a sense-mode could dominate over the Coriolis response.
Practically, fabrication imperfections may result in less-than-ideal geometries in structures such as gyroscope structures. Less-than-ideal geometries can cause a drive oscillation to partially couple into a sense-mode. Even though several cross-coupling approaches exist, such as elastic, viscous and electrostatic coupling approaches, in certain cases the elastic coupling due to anisoelasticity in the suspension elements increases in magnitude beyond a desired level.
In sensor systems such as gyroscope systems with out-of-plane operational modes, anisoelasticity between the in-plane and out-of-plane directions is the dominating source of Quadrature error. Sidewall tilt or skew in deep reactive-ion etching (“DRIE”) can result in deviation of the cross-section of the flexure bearings from a rectangle to a parallelogram, causing the principle axes of elasticity of the suspension flexure bearings to deviate from parallel and orthogonal to the device surface. In an example, single or multi-axis micromachined sensor structures such as gyroscope structures can suffer from high-quadrature error caused at least in part by DRIE skew.
Additionally, prior resonators rely on simple straight flexure bearings to generate a flexing structure to allow the device to displace in resonance. This creates significant problems when etching creates a skew in the flexure bearing, causing large undesired displacement, often actuating a sense mechanism.